Troubleshooting Odd Power Loss in a Passive System

Hey everyone - it's been a while since I've been on here. Hope everyone is hanging in there and doing well.

I'm encountering some odd issues with one of my older systems I have having difficulty tracing. Before everyone starts hating on the gear - this is NOT one of my wedding rigs - it is the system that goes out to outdoor events and lives half the year at a farm.

So...the equipment with issues is a rack of Crown CE1000s and some Peavey PVDJS4's. Again - I know it's older and not higher end, but it serves its purpose in the fact that I leave this rig behind places and use it at outdoor gigs without really worrying about it. Up until recently, the system was rock solid and (in my opinion) sounded great for what it was.

It went out to a grad party this year with no issues. We then received a contract for a series of events at a drive-in movie theatre. The first gig it held up great and covered the entire area nicely. The second gig, I noticed I was having to drive it wayyyy harder than usual and wasn't getting it's regular "punch" and output. I took everything back with me and tested it and found one of the CE1000s appeared to have a bad Channel 1. I stuck a QSC PLX series amp in and put the one CE1000 in the repair pile. Next gig - still having to drive it wayyy harder than usual and while it covered the gig I noticed distortion that seemed out of the norm for the system. I figured perhaps another CE1000 was on it's way out, so I took the entire thing back with me and tested the speakers with newer amps and a different mixer. On the bench with the newer amp, it was still initially acting up - indicative of a speaker issue. I messed with it for a while and couldn't tell you what I did but it once again seems to be working fine here.

I took the speakers apart - tested the cables, jacks, capacitors, lamp/fuse and checked all connections. Everything seems fine. Now I'm stumped. Does anyone have any ideas what might cause something like this?

steve149 said:

Have you tried the amps with other speakers? Sounds like a crossover/fusing issue, but not sure if they test OK. I might also check the voice coils on the woofers .. high heat in use or storage can cause the coils to shift and might build up friction and loss of power.

Click to expand...

Yes - I did test the amps with other speakers which is how I was able to rule the CE1000 as part of the issue (I'm actually running 4 of these speakers).

I'm guessing it may be the voice coils. What is the proper procedure to check them? I did notice the impedance was slightly off but chalked it up to a cheap multimeter for what its worth.

Side note: the coils would make sense as this is the system that gets heavily abused.

So I had some weddings cancel this last weekend and ended up running the speakers personally at a festival. So the entire thing was being run on a completely different rack than any used to-date. One speaker sounded fine. The other sounded scratchy - moreso scratchy through the horn (rx22) when the bass would "hit". The bass also seemed weaker (scorpion 15) - which seems to support what many of you are saying. While my first suspicion would be a capacitor - the capacitor is fine. I opened up the speaker to take a look around. One thing I did notice was there was no "lamp" and it was bypassed with a 250v fuse. Not sure if this is common with these or if someone had repaired or modded them at some point. I do have continuity across the fuse. While I don't believe the bypass to be factory I can't say for sure - the fuse is actually in a holder and soldered, but it looks like it is attached with consumer grade speaker wire. If someone did actually mod these I can't entirely blame them as I too have personally bypassed the protection lamps on some of my older Peavey speakers.

As for some of the other questions:
-I'd imagine these speakers are probably 15 years old. Up until recently they sounded great.
-Yes they are abused since aesthetically they will never see another wedding or high end event (they've gotten wet at festivals and Relay for Life, been stored in outdoor non-climate controlled storage as well as a greenhouse in the fall and been in and out of my truck countless times since I've acquired them)

They still sounded "passable" for the job they were doing - just to my trained ear I can tell something is not right.

I'd like to get one more season out of them if I can do it on the cheap - as a larger pair of QSCs or the ETXs with dual 15s are a little out of the question with the hit we took this year along with the fact I have a lot of money locked up in other things at the moment.

I know I've tested speakers manually by hand before listening for a "grinding" noise when applying pressure by hand to the cone. I don't know that these are to that point where it will be audible from the bench. I see a couple of you have sent some good tips on how to test manually. Would issues with the coil affect impedance? How can I tell if I have a shifted magnet?

I may finish my diagnosis with just swapping parts from one speaker to the other to see if a particular component is causing issues.

PS - Thanks for the welcome back everyone. I will try to get some pictures of the rig up soon (although this setup is not representative of what we normally send out)